1. Field of the Invention
The present invention relates to improvements of a crimping device for crimping crimp pieces of a metal terminal in which the improvement of electrical connection performance is made by increasing the mechanical clamp strength.
The present application is based on Japanese Patent Application No. 2000-059037, which is incorporated herein by reference.
2. Description of the Related Art
In a case where a covered wire is connected to a metal terminal by crimping, the covered wire with a covering at its tip portion peeled off is placed in such a manner as to be sandwiched between a pair of front legs and a pair of rear legs, respectively, which are crimp pieces of the metal terminal, and are crimped by a clamping motion of a crimping device, thereby making it possible to obtain electrical connection performance with predetermined mechanical strength.
For example, in a case where a female metal terminal 2 is crimped and fixed to a covered wire 1 shown in FIG. 5, a pair of front legs 3 of the female metal terminal 2 are clamped against a core strand 4 and a pair of rear legs 5 against a covered portion 6, respectively, thereby forming a conductor crimped portion 7 and a covering crimped portion 8. The metal terminal 2 with a wire thus obtained is used by being electrically connected by being inserted into an inserting portion of an unillustrated connector body.
The crimping of the crimp pieces of this metal terminal is effected by a crimping device shown in FIGS. 6A to 6C. Namely, the pair of curved front legs 3 are placed on a crimp anvil 9, and the core strand 4 is placed in it (FIG. 6A). Meanwhile, a crimp indenter 10 (hereafter referred to as the “crimper”) has two arch-shaped portions which are bilaterally symmetrical, and each of the arch-shaped portions has a curved surface formed continuously with two different radii of curvatures R1 and R2. As this crimper 10 is lowered, the conductor crimped portion 7 such as the one shown in FIG. 6B is formed by clamping.
However, since the radius of curvature R1 is smaller than the radius of curvature R2, when the front legs 3 are crimped, a component of force FX of a crimping force F, which is larger than a component of force FY thereof, is applied to a tip of each of the front legs 3 in a mutually interfering direction, as shown in FIG. 6C. For this reason, the force FY with which the tips of the front legs bite into the core strand 4 becomes weak correspondingly, and it becomes difficult to obtain predetermined clamp strength, thereby possibly causing a decline in the reliability of electrical connection correspondingly.
This also applies to a case in which, as shown in FIGS. 7A to 7C, the inner surface of the crimper 10 is formed with a single radius of curvature R3, the component of force FX larger than the component of force FY is applied to the tip of each of the front legs 3, as shown in FIG. 7C. For this reason, since this component of force FX acts in the direction in which the two tips interfere with each other, the biting into the core strand 4 becomes shallow in the same way as FIGS. 6A to 6C, possibly leading to the impairment of the reliability.